Method, device, and system for pre-authentication

ABSTRACT

The present invention relates to mobile communications technologies, and discloses a method, device, and system for pre-authentication. A pre-authentication device receives a pre-authentication message that carries a pre-authentication option; determines a Mobile Node (MN) to be pre-authenticated according to the pre-authentication message; sends an authentication request message to an Authentication, Authorization and Accounting (AAA) server to request authentication of the MN; receives an authentication response message that is sent by the AAA server, where the authentication response message carries a pre-authentication key used between a Candidate Authenticator (CA) and the MN; and sends the pre-authentication key to the MN. Through implementation of the present invention, the pre-authentication key is obtained before the MN switches to the CA. In this way, security of communication is enhanced, and delay of switching and authentication is shortened.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2010/071115, filed on Mar. 18, 2010, which claims priority toChinese Patent Application No. 200910106152.9, filed on Mar. 18, 2009,both of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to mobile communication technologies, andin particular, to a method, device, and system for pre-authentication ina multi-authenticator scenario.

BACKGROUND

Extensible Authentication Protocol (EAP) architecture generally includesa client, an authenticator, and an Authentication, Authorization andAccounting (AAA) server/EAP server. The authenticator is generallylocated at the edge of a network, and is coupled with the AAA server/EAPserver, or is stand-alone. This architecture provides a function ofauthenticating and authorizing client devices. An EAP method in EAP isdesigned to generate a key material such as a Master Session Key (MSK)and an Extended Master Session Key (EMSK). The MSK is applied to alower-layer protocol below the EAP, and the EMSK is used to protectinteraction between a client and the AAA server. Because a complete EAPprocess generally involves more than two round trips of interaction,delay of authentication and authorization is generally long. A mechanismof reusing a key and state information generated in initialauthentication and avoiding use of an asymmetrical key is taken toreduce such switching delay in many measures. However, the extent ofimprovement of the number of the times of interaction varies dependingon the EAP method in use. Regardless of the extent of improvement, anauthentication and authorization process is completed only after atleast two round trips of interaction are complete. The switching delayis not acceptable to certain real-time applications.

To support quick switching, complete AAA-based authentication isgenerally avoided. A complete authentication process involves multipleround trips of interaction with a home AAA server of a Mobile Node (MN),which leads to long switching delay. Common EAP authentication methodsused in quick switching include EAP re-authentication and EAPpre-authentication. A conception of the EAP re-authentication is: alocal EAP server mechanism is introduced, and the key material used ininitial complete authentication is reused to avoid too many EAP-basedAAA messages in a switching process of the mobile terminal. A conceptionof the EAP pre-authentication is: an MSK is generated before switchingof the mobile terminal, and is used for authentication between themobile terminal and a Candidate Authenticator (CA).

In the process of developing the present invention, the inventor findsthat the prior art has the following problems:

In the process of interaction between an EAP client and an AAA server,it is generally necessary to traverse two authenticators, namely, aServing Authenticator (SA) and a CA. In this case, the SA and the CA areunable to judge whether an authentication request sent by the client isan ordinary authentication request or a pre-authentication request, andunable to judge whether the SA and the CA themselves need to interactwith the AAA server to complete a pre-authentication process, whichleads to a pre-authentication failure and switching delay.

SUMMARY

Embodiments of the present invention provide a method, device, andsystem for pre-authentication. Through implementation of the presentinvention, an SA and a CA can correctly identify a pre-authenticationmessage, and use a pre-authentication key obtained in apre-authentication process to protect communication between an MN andthe CA. In this way, security of communication is enhanced, and delay ofswitching and authentication is shortened.

A pre-authentication method provided in an embodiment of the presentinvention includes: receiving a pre-authentication message that carriesa pre-authentication option; determining an MN to be pre-authenticatedaccording to the pre-authentication message; sending an authenticationrequest message to an AAA server to request authentication of the MN,where the authentication request message carries the pre-authenticationoption; receiving an authentication response message that is sent by theAAA server, where the authentication response message carries apre-authentication key used between a CA and the MN; and sending thepre-authentication key to the MN.

A pre-authentication device provided in an embodiment of the presentinvention includes: a first receiving unit, configured to receive apre-authentication message that carries a pre-authentication option; adetermining unit, configured to determine an MN to be pre-authenticatedaccording to the pre-authentication message; a first sending unit,configured to send an authentication request message to an AAA server torequest authentication of the MN, where the authentication requestmessage carries the pre-authentication option; a second receiving unit,configured to receive an authentication response message that is sent bythe AAA server, where the authentication response message carries apre-authentication key used between a CA and the MN; and a secondsending unit, configured to send the pre-authentication key to the MN.

A pre-authentication system provided in an embodiment of the presentinvention includes a pre-authentication device and an AAA server. Thepre-authentication device is configured to: receive a pre-authenticationmessage that carries a pre-authentication option; determine an MN to bepre-authenticated according to the pre-authentication message; send anauthentication request message to an AAA server to requestauthentication of the MN, where the authentication request messagecarries the pre-authentication option; receive an authenticationresponse message that is sent by the AAA server, where theauthentication response message carries a pre-authentication key usedbetween a CA and the MN; and send the pre-authentication key to the MN.The AAA server is configured to: receive the authentication requestmessage that is sent by the pre-authentication device; generate thepre-authentication key used between the CA and the MN according to theauthentication request message; add the pre-authentication key to theauthentication response message; and send the authentication responsemessage to the pre-authentication device.

Through implementation of the present invention, the SA or the CA cancorrectly identify a pre-authentication message; after receiving thepre-authentication message, the SA or the CA obtains thepre-authentication key, used between the CA and the MN, from the AAAserver; when the MN switches to the CA, the pre-authentication key maybe used to protect the communication between the MN and the CA. In thisway, security of communication is enhanced, and delay of switching andauthentication is shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

To make technical solutions of the present invention clearer, theaccompanying drawings for illustrating embodiments of the presentinvention are outlined below. Evidently, the accompanying drawings areonly exemplary, and those skilled in the art can derive other drawingswithout any creative effort.

FIG. 1 is a schematic flowchart of a pre-authentication method accordingto an embodiment of the present invention;

FIG. 2A and FIG. 2B are schematic flowcharts of a pre-authenticationmethod according to another embodiment of the present invention;

FIG. 3 is a schematic flowchart of a pre-authentication method accordingto another embodiment of the present invention;

FIG. 4 is a schematic flowchart of a pre-authentication method accordingto another embodiment of the present invention;

FIG. 5 is a schematic flowchart of a pre-authentication method accordingto another embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a pre-authentication deviceaccording to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a pre-authentication deviceaccording to another embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a pre-authentication deviceaccording to another embodiment of the present invention; and

FIG. 9 is a schematic structural diagram of a pre-authentication systemaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

The embodiments of the present invention are detailed below withreference to the accompanying drawings.

FIG. 1 is a schematic flowchart of a pre-authentication method accordingto an embodiment of the present invention. The method includes thefollowing steps:

10. Receive a pre-authentication message that carries apre-authentication option.

The pre-authentication message may be sent by an MN that serves as aclient, or by an SA of the MN. The pre-authentication option may be apre-authentication start (Pre-auth Start) flag or a CA identifier(CA_ID) which indicates a purpose of the pre-authentication message.

11. Determine an MN to be pre-authenticated according to thepre-authentication message.

If the pre-authentication message is sent by the MN, the source node ofthe pre-authentication message is the MN to be pre-authenticated; if thepre-authentication message is sent by the SA, the MN to bepre-authenticated is determined according to content of thepre-authentication message.

12. Send an authentication request message to the AAA server, where theauthentication request message carries the pre-authentication option.The authentication request message requests the AAA server toauthenticate the MN that serves as the client, and generate apre-authentication key used between a CA and the MN. The authenticationrequest message needs to carry a pre-authentication option. Thepre-authentication option is the same as the pre-authentication optiondescribed in step 10, and specifically, may be a CA_ID. The CA_ID may becarried in a pre-authentication option, or an independent option.

13. Receive an authentication response message that is sent by the AAAserver, where the authentication response message carries thepre-authentication key used between the CA and the MN. Aftersuccessfully authenticating the MN, the AAA server generates thepre-authentication key used between the CA and the MN according to thepre-authentication option and other key materials. In addition, the AAAserver sends the authentication response message that carries thepre-authentication key to the CA.

14. Send the received pre-authentication key to the MN that serves as aclient.

The pre-authentication key is sent by the SA to the MN. After receivingthe pre-authentication key, the MN determines that thepre-authentication with the CA is complete.

If the step of receiving the pre-authentication message is performed bythe CA, a step of establishing a pre-authentication binding relationshipmay occur between step 11 and step 12. Specifically, the CA establishesa pre-authentication binding relationship between the CA and the MN, andmarks an authentication state of the MN as pre-authenticated accordingto the pre-authentication message.

In this embodiment, the pre-authentication key includes thepre-authentication key used between the CA and the MN, and an MSK and anEMSK used between the MN and the AAA server.

Through implementation of this embodiment, after receiving anauthentication message, the CA determines that the message is apre-authentication message according to the pre-authentication optioncarried in the message, and initiates a pre-authentication process. Inthis case, a process of authenticating the MN is complete before the MNis attached to the CA. When the MN switches to the CA, thepre-authentication key may be used to quickly authenticate the MN, whichshortens delay of switching and authentication.

The method shown in FIG. 1 is applicable when multiple authenticators(one SA and multiple CAs) exist at the time of switching the MN. Thefollowing describes how the method works in such scenarios.

FIG. 2A and FIG. 2B show another embodiment of the pre-authenticationmethod. In this embodiment, an SA or an MN is responsible fordiscovering a CA. That is, the SA or the MN obtains a CA_ID by using adiscovery mechanism before start of pre-authentication. The CA_ID may bean IP address of the CA, a domain name of the CA, or another identifier(ID) that uniquely identifies the CA. In the pre-authentication, the SAundertakes a function of an Authenticator Relay. The method in thisembodiment includes the following steps:

20. The MN initiates a pre-authentication request to the SA. Thepre-authentication request carries a pre-authentication option, andrequests the SA to select the CA for the MN. The pre-authenticationoption is a Pre-auth Start flag or a CA_ID. It should be noted that thisstep is optional. When this step occurs, the pre-authentication isinitiated by the MN; if this step is omitted, the pre-authentication isinitiated by a network.

21. The SA sends a pre-authentication initiation message to the MN,requesting the MN to confirm whether to initiate the pre-authentication.In this step, the SA may send the pre-authentication initiation messageto the MN actively, or as requested by the MN. The pre-authenticationinitiation message carries a pre-authentication option. Thepre-authentication option is a Pre-auth Start flag. Thepre-authentication initiation message may carry a CA_ID (if the SAdiscovers the CA), or carries no CA_ID (if the MN discovers the CA). Thepre-authentication initiation message may be an EAP initiation(EAP-Initiate) message or an EAP request (EAP-Req) message that carriesthe Pre-auth Start flag.

22. The MN sends a pre-authentication confirmation message to the SAaccording to the pre-authentication initiation message that is sent bythe SA, where the pre-authentication confirmation message carries apre-authentication option. The pre-authentication option may be apre-authentication indication (Pre-auth Indication) flag, whichindicates whether the initiated authentication is pre-authentication orordinary authentication. The pre-authentication confirmation messagecarries a CA_ID which indicates the CA to be pre-authenticated. Thepre-authentication confirmation message may be an EAP-Initiate messageor an EAP-Rsp message that carries the Pre-auth Indication flag.

23. The SA determines the CA according to the CA_ID carried in thepre-authentication confirmation message. The CA_ID is carried in anextended Peer_ID option (Peer_ID@CA_ID) of the EAP-Initiate message orthe EAP-Rsp message, or carried in an independent CA_ID option.

24. The SA forwards the pre-authentication confirmation message to theCA which is determined according to the pre-authentication confirmationmessage. When the SA sends this message, the EAP-Initiate message or theEAP-Rsp message that serves as the pre-authentication confirmationmessage may be sent over a layer-3 protocol. The SA does not modifycontent of the pre-authentication confirmation message when forwardingthe message.

25. After receiving the pre-authentication confirmation message, the CAlocally establishes a pre-authentication binding relationship andpre-authentication state, that is, establishes a binding relationshipbetween the MN and the CA, and marks an authentication state of the MNas pre-authenticated. In this step, the CA may confirm that the messageis a pre-authentication confirmation message according to thepre-authentication option, for example, the extended option(Peer_ID@CA_ID) of the Peer_ID or the Pre-auth Indication flag, in themessage.

26. The CA sends an authentication request message to an AAA server,requesting the AAA server to authenticate the MN. The authenticationrequest message carries a pre-authentication option and an MN ID. The MNID may be a Network Access Identifier (NAI) or a home domain name of theMN.

27. After receiving the authentication request message that is sent bythe CA, the AAA server authenticates the MN. After the authenticationsucceeds, the AAA server generates a pre-authentication key used betweenthe CA and the MN, and sends an authentication response message to theCA. The authentication response message carries the generatedpre-authentication key used between the CA and the MN.

28. After receiving the authentication response message that is sent bythe AAA server, the CA obtains and stores the pre-authentication keycarried in the message.

29-210. Through the SA, the CA sends a pre-authentication successmessage to the MN that sends the pre-authentication confirmationmessage. The pre-authentication success message carries thepre-authentication key that is sent by the AAA server, and the messagemay be an EAP-Finish message or an EAP-Success message that carries thepre-authentication key.

211. After receiving the pre-authentication success message that is sentby the SA, the MN obtains and stores the pre-authentication key carriedin the message. After obtaining the pre-authentication key, the MNcompletes the pre-authentication with the AAA server. After beingattached to the CA, the MN can use the pre-authentication key to protectcommunication between the MN and the CA.

In this embodiment, the AAA server may also generate an MSK and an EMSKfor authentication between the AAA server and the MN. The MSK and theEMSK may also be sent by the AAA server to the MN through the CA.

In this embodiment, the SA sends a pre-authentication message to the CAaccording to the selection made by the MN; the CA locally establishes apre-authentication binding relationship with the MN; after the AAAserver successfully authenticates the MN that serves as a client, thepre-authentication key generated by the AAA server is sent to the MN andthe CA to complete the pre-authentication between the MN and the AAAserver. In this way, when the MN switches to the CA, the MN can use thereceived pre-authentication key to protect the communication between theMN and the CA, and delay of switching and authentication is shortened.

In the pre-authentication method in this embodiment, thepre-authentication may also be initiated by the CA as indicated by theSA. FIG. 3 shows another embodiment of the pre-authentication method. Inthis embodiment, an SA is responsible for discovering a CA. The methodin this embodiment includes the following steps:

30. The SA sends a pre-authentication initiation indication message tothe CA, where the pre-authentication initiation indication messagecarries a pre-authentication option. The pre-authentication option maybe a Pre-auth Indication flag, which indicates whether the initiatedauthentication is pre-authentication or ordinary authentication. Thepre-authentication initiation indication message further carries an MNID. The MN ID may be an address of an MN, a domain name of the MN, or aPeer_ID of the MN.

31. After receiving the pre-authentication initiation indicationmessage, the CA sends a pre-authentication initiation message to the MNaccording to the MN ID carried in the pre-authentication initiationindication message. The pre-authentication initiation message carries apre-authentication option, and may be an EAP-Initiate message or anEAP-Req message that carries a Pre-auth Start flag.

32. The MN sends a pre-authentication confirmation message to the CAaccording to the pre-authentication initiation indication message thatis sent by the CA, where the pre-authentication confirmation messagecarries the pre-authentication option. The pre-authenticationconfirmation message is specifically an EAP-Initiate message or anEAP-Rsp message that carries a Pre-auth Indication flag.

33. After receiving the pre-authentication confirmation message, the CAlocally establishes a corresponding pre-authentication bindingrelationship and pre-authentication state, that is, establishes abinding relationship between the MN and the CA, and marks anauthentication state of the MN as pre-authenticated.

Steps 34-39 in this embodiment are basically the same as steps 26-211shown in FIG. 2A and FIG. 2B, and are not further described.

In this embodiment, the SA automatically discovers a possible CA, andinstructs the CA to initiate pre-authentication to the MN, which avoidsdelay of switching and authentication caused when the CA is not surewhether the pre-authentication message received from the MN is anordinary message or a pre-authentication message.

In another embodiment of the present invention, an SA may replace a CAto send a request to an AAA server for initiating a process ofpre-authenticating an MN. FIG. 4 is a schematic flowchart of apre-authentication method according to another embodiment of the presentinvention. In this embodiment, the SA or the MN is responsible fordiscovering the CA. That is, the SA or the MN obtains a CA_ID by using adiscovery mechanism before start of pre-authentication. The CA_ID may bean IP address of the CA, a domain name of the CA, or another ID thatuniquely identifies the CA. The method includes the following steps:

40. The MN initiates a pre-authentication request to the SA. Thepre-authentication request may carry a pre-authentication option, andrequests the SA to select the CA for the MN. It should be noted thatthis step is optional. When this step occurs, the pre-authentication isinitiated by the MN; if this step is omitted, the pre-authentication isinitiated by a network.

41. The SA sends a pre-authentication initiation message to the MN. Inthis step, the SA may send the pre-authentication initiation message tothe MN actively, or as requested by the MN. The pre-authenticationinitiation message carries a pre-authentication option. Specifically,the pre-authentication initiation message may carry a Pre-auth Startflag, which requests the MN to confirm whether to initiatepre-authentication. The pre-authentication initiation message may carrya CA_ID (if the SA discovers the CA), or carries no CA_ID (if the MNdiscovers the CA). The pre-authentication initiation message may be anEAP-Initiate message or an EAP-Req message that carries the Pre-authStart flag.

42. The MN sends a pre-authentication confirmation message to the SAaccording to the pre-authentication initiation message that is sent bythe SA, where the pre-authentication confirmation message carries apre-authentication option. Specifically, the pre-authenticationconfirmation message may carry a Pre-auth Indication flag that indicateswhether the initiated authentication is pre-authentication or ordinaryauthentication. The pre-authentication confirmation message carries aCA_ID that indicates the CA selected by the MN. The pre-authenticationconfirmation message may be an EAP-Initiate message or an EAP-Rspmessage that carries the Pre-auth Indication flag.

43. The SA determines the CA according to the receivedpre-authentication confirmation message.

44. The SA sends an authentication request message to the AAA server.The authentication request message carries an extended Peer_ID option(which carries a Peer_ID and the CA_ID) and other pre-authenticationoptions, and requests the AAA server to pre-authenticate the MN.

45. After receiving the authentication request message that is sent bythe SA, the AAA server authenticates the MN that serves as a client, andextracts the CA_ID. After successfully authenticating the MN, the AAAserver generates a pre-authentication key between the CA and the MN, andsends an authentication response message to the CA. The authenticationresponse message carries the generated pre-authentication key.

Steps 46-49 in this embodiment are basically the same as steps 28-211shown in FIG. 2A and FIG. 2B, and are not further described.

In this embodiment, after receiving the pre-authentication confirmationmessage that is sent by the MN, the SA replaces the CA to send a requestto the AAA server for pre-authenticating the MN, and the AAA serverdistributes the pre-authentication key to the MN and the CA. When the MNswitches to the CA, the pre-authentication key distributed by the AAAserver may be used to perform quick authentication, which shortens thedelay of switching and authentication.

In this embodiment, the MN may be responsible for discovering the CA,that is, obtaining the CA_ID, and the MN initiates a pre-authenticationprocess after discovering the CA. FIG. 5 is a schematic flowchart of theMN actively initiating a pre-authentication process according to anembodiment of the present invention. The process includes the followingsteps:

50. An MN sends a pre-authentication initiation message to an SA, wherethe pre-authentication initiation message carries a pre-authenticationoption. Specifically, the pre-authentication initiation message may bean EAP-Initiate message or an EAP-Req message that carries a CA_ID or alayer-2 link ID (BS_ID) corresponding to a CA. The CA_ID or the BS_IDmay be an independent option of the pre-authentication initiationmessage, or is an extended option (in the form of Peer_ID@CA_ID orPeer_ID@BS_ID) of a Peer_ID.

51. After receiving the pre-authentication initiation message, the SAconfirms that the message is a pre-authentication initiation messageaccording to the CA_ID or the BS_ID carried in the message, and obtainsthe CA directly or by querying a mapping relationship between thelayer-2 link ID and a layer-3 link ID (if the message carries theBS_ID). Without changing the message, the SA sends the message to the CAover a layer-3 protocol.

52. The CA determines that the pre-authentication initiation message isa pre-authentication request according to the pre-authentication optionin the received pre-authentication initiation message, and locallyestablishes a corresponding pre-authentication binding relationship andpre-authentication state, that is, establishes a binding relationshipbetween the MN and the CA, and marks an authentication state of the MNas pre-authenticated.

Steps 53-58 in this embodiment are the same as the steps 26-211 shown inFIG. 2A and FIG. 2B, and are not further described.

In this embodiment, the MN actively initiates pre-authentication afterdiscovering the CA or the BS_ID. In this way, a pre-authentication keybetween the CA and the MN is distributed, and the delay of switching andauthentication is shortened.

An embodiment of the present invention provides a pre-authenticationdevice. The pre-authentication device may act as an SA or a CA describedin the preceding method embodiments.

FIG. 6 is a schematic structural diagram of a pre-authentication deviceaccording to an embodiment of the present invention. Apre-authentication device 60 is configured to initiatepre-authentication of an MN. A first receiving unit 610 is configured tosend a pre-authentication message to a determining unit 620 afterreceiving the pre-authentication message that carries apre-authentication option. The determining unit 620 determines an MN tobe pre-authenticated according to a source node of thepre-authentication message or the pre-authentication option carried inthe pre-authentication message. Afterward, a first sending unit 630sends an authentication request message to an AAA server, requesting theAAA server to pre-authenticate the MN. The authentication requestmessage carries a pre-authentication option and an ID of the MN to bepre-authenticated, and also needs to carry a CA_ID. The CA_ID may becarried in the pre-authentication option or another option. Aftersuccessfully authenticating the MN, the AAA server generates apre-authentication key used between the MN and the CA according to thepre-authentication option, and sends the pre-authentication key to asecond receiving unit 650 through an authentication response message.After receiving the pre-authentication key that is sent by the AAAserver, the second receiving unit 650 sends the pre-authentication keyto a second sending unit 640, and the second sending unit 640 sends thepre-authentication key to the MN. In this way, the pre-authenticationkey is distributed.

In the embodiment shown in FIG. 6, two or more units may be setseparately, or integrated in one module. For example, the firstreceiving unit 610 and the second receiving unit 650 may be integratedin a receiving module; the first sending unit 630 and the second sendingunit 640 may be integrated in a sending module; the first receiving unit610, the second receiving unit 650, the first sending unit 630, and thesecond sending unit 640 may be integrated in a receiving and sendingmodule.

In the case that the pre-authentication device 60 acts as an SA, thestructure of the pre-authentication device provided in anotherembodiment of the present invention is shown in FIG. 7. Thispre-authentication device 60 includes at least a discovering unit 660 inaddition to the units shown in FIG. 6. The discovering unit 660 isconfigured to discover the CA of the MN. The first sending unit 630 isfurther configured to send a pre-authentication initiation message tothe MN, where the pre-authentication initiation message carries an ID ofthe discovered CA. The pre-authentication initiation message may be anEAP-Initiate message or an EAP-Req message that carries a Pre-auth Startflag. In this case, the pre-authentication message received by the firstreceiving unit 610 is a pre-authentication confirmation message that issent by the MN and carries the ID of the selected CA, and isspecifically an EAP-Initiate message or an EAP-Rsp message that carriesa Pre-auth Indication flag.

In the case that the pre-authentication device 60 acts as a CA describedin the preceding method embodiments, the structure of thepre-authentication device provided in another embodiment of the presentinvention is shown in FIG. 8. The pre-authentication device 60 includesat least a binding unit 670 and a storing unit 680 in addition to theunits shown in FIG. 6. After the determining unit 620 determines the MNto be pre-authenticated according to the pre-authentication message, thebinding unit 670 locally establishes a binding relationship between theCA and the MN, and sets the authentication state of the MN aspre-authenticated. After receiving the authentication response messagethat is sent by the AAA server, the second receiving unit 650 obtainsthe pre-authentication key from the message, and sends thepre-authentication key to the storing unit 680. The storing unit 680 isconfigured to store the pre-authentication key. In this way, when the MNswitches to the CA, the stored pre-authentication key may be used toquickly authenticate the MN, which shortens delay of switching andauthentication.

When the pre-authentication device 60 is a CA, the pre-authenticationmessage may be:

an EAP-Initiate message or an EAP-Rsp message that is sent by the SA andcarries a Pre-auth Indication flag or a CA_ID; or

an EAP-Initiate message or an EAP-Rsp message that is sent by the MN andcarries a Pre-auth Indication flag or a CA_ID; or

an EAP-Initiate message or an EAP-Req message that is sent by the SA andcarries a CA_ID or a BS_ID corresponding to the CA.

In this embodiment, after receiving a pre-authentication message, thepre-authentication device requests the AAA server to authenticate the MNaccording to the pre-authentication option and the MN associatedinformation in the pre-authentication message, and receives apre-authentication key between the MN and the CA from the AAA server. Inthis way, when the MN switches to the CA, the pre-authentication key maybe used to protect the communication between the MN and the CA, anddelay of switching and authentication is shortened.

An embodiment of the present invention discloses a pre-authenticationsystem. The pre-authentication system 90 includes a pre-authenticationdevice 910 and an AAA server 920. When the pre-authentication systemruns, the pre-authentication device 910 receives a pre-authenticationmessage from an SA or an MN, where the pre-authentication messagecarries a pre-authentication option. The pre-authentication device 910determines the MN to be pre-authenticated according to thepre-authentication message. If the pre-authentication message isreceived from an MN, the MN to be pre-authenticated is the MN that sendsthe pre-authentication message; if the pre-authentication message isobtained from the SA, the pre-authentication message needs to carryinformation about the MN to be pre-authenticated, and the MN to bepre-authenticated is determined according to the information carried inthe pre-authentication message. The pre-authentication option carried inthe pre-authentication message includes a Pre-auth Indication flag or aCA_ID. The pre-authentication device 910 sends an authentication requestmessage to the AAA server 920 according to the pre-authenticationmessage, requesting authentication of the MN to be pre-authenticated.The authentication request message carries a pre-authentication optionthat is the same as the pre-authentication option carried in thepre-authentication message, and the pre-authentication option indicatesthat the authentication of the MN is pre-authentication.

After receiving the authentication request message, the AAA server 920authenticates the MN according to the authentication request message.After the authentication succeeds, the AAA server generates apre-authentication key between a CA and the MN according to thepre-authentication option in the authentication request message, addsthe pre-authentication key to an authentication response message, andsends the authentication response message to the pre-authenticationdevice 910. The pre-authentication device 910 sends thepre-authentication key to the MN (not shown in FIG. 9).

The pre-authentication device 910 may be the SA or the CA of the MN.When the pre-authentication device 910 is the SA, the pre-authenticationdevice can discover the CA of the MN, and initiate a pre-authenticationprocess as requested by the MN or according to a policy. Thepre-authentication device 910 obtains the pre-authentication key betweenthe CA and the MN from the AAA server through the CA of the MN. When thepre-authentication device 910 is the CA, the pre-authentication devicecan establish a pre-authentication binding relationship between the MNand the pre-authentication device, and set an authentication state ofthe MN as pre-authenticated according to the received pre-authenticationrequest. Moreover, the pre-authentication device can store thepre-authentication key and send the pre-authentication key to the MNthrough the SA after receiving the pre-authentication key that is sentby the AAA server.

Through implementation of the present invention, the SA or the CA cancorrectly identify a pre-authentication message; after receiving thepre-authentication message, the SA or the CA obtains thepre-authentication key used between the CA and the MN from the AAAserver; when the MN switches to the CA, the pre-authentication key maybe used to protect communication between the MN and the CA. In this way,security of communication is enhanced, and delay of switching andauthentication is shortened.

Persons of ordinary skill in the art should understand that all or partof the steps of the methods provided in the preceding embodiments may beimplemented by a computer program instructing relevant hardware. Theprogram may be stored in computer readable storage media. When beingexecuted, the program may perform steps of a method specified in anypreceding embodiment. The storage media may be a magnetic disk, aCompact Disk-Read Only Memory (CD-ROM), a Read Only Memory (ROM), or aRandom Access Memory (RAM).

The preceding descriptions are merely exemplary embodiments of thepresent invention, and not intended to limit the protection scope of thepresent invention. Any modification, variation, or replacement that canbe easily derived by those skilled in the art shall fall within theprotection scope of the present invention. Therefore, the protectionscope of the present invention is subject to the appended claims.

What is claimed is:
 1. A pre-authentication method, comprising: receiving a pre-authentication message that carries a pre-authentication option; determining, according to the pre-authentication message, a Mobile Node (MN) to be pre-authenticated; establishing a pre-authentication binding relationship between a Candidate Authenticator (CA) and the MN, and setting an authentication state of the MN as pre-authenticated according to the pre-authentication message; sending an authentication request message to an Authentication, Authorization and Accounting (AAA) server to request authentication of the MN, wherein the authentication request message carries the pre-authentication option; receiving an authentication response message that is sent by the AAA server, wherein the authentication response message carries a pre-authentication key used between the CA and the MN; and sending the pre-authentication key to the MN; wherein: the pre-authentication message is an Extensible Authentication Protocol (EAP) initiation (EAP-Initiate) message or an EAP response (EAP-Rsp) message that is sent by a Serving Authenticator (SA) and carries a pre-authentication indication (Pre-auth Indication) flag or a CA identifier (CA_ID).
 2. The method according to claim 1, wherein: before the receiving the pre-authentication message, the method further comprises: sending, by the SA, an EAP-Initiate message that carries a Pre-auth Start flag to the MN, and receiving the EAP-Initiate message that is sent by the MN and carries the Pre-auth Indication flag or a CA_ID; or sending, by the SA, an EAP request (EAP-Req) message that carries the Pre-auth Start flag to the MN, and receiving the EAP-Rsp message that is sent by the MN and carries the Pre-auth Indication flag or the CA_ID.
 3. A pre-authentication method, comprising: receiving a pre-authentication message that carries a pre-authentication option; determining, according to the pre-authentication message, a Mobile Node (MN) to be pre-authenticated; establishing a pre-authentication binding relationship between a Candidate Authenticator (CA) and the MN, and setting an authentication state of the MN as pre-authenticated according to the pre-authentication message; sending an authentication request message to an Authentication, Authorization and Accounting (AAA) server to request authentication of the MN, wherein the authentication request message carries the pre-authentication option; receiving an authentication response message that is sent by the AAA server, wherein the authentication response message carries a pre-authentication key used between the CA and the MN; and sending the pre-authentication key to the MN; wherein: the pre-authentication message is an Extensible Authentication Protocol (EAP) initiation (EAR-Initiate) message or an EAP response (EAP-Rsp) message that is sent by the MN and carries a Pre-auth Indication flag or a CA identifier (CA_ID).
 4. The method according to claim 3, wherein: before the receiving the pre-authentication message, the method further comprises: receiving a pre-authentication initiation indication message that is sent by a Serving Authenticator (SA) and carries an MN identifier (ID); sending an EAP-Initiate message or an EAP request (EAP-Req) message that carries a Pre-auth Start flag to the MN according to the pre-authentication initiation indication message; and receiving the EAP-Initiate message or the EAP-Rsp message that is sent by the MN and carries the Pre-auth Indication flag or the CA_ID.
 5. A pre-authentication device, comprising: a first receiving unit, configured to receive a pre-authentication message that carries a pre-authentication option; a determining unit, configured to determine a Mobile Node (MN) to be pre-authenticated according to the pre-authentication message; a first sending unit, configured to send an authentication request message to an Authentication, Authorization and Accounting (AAA) server to request authentication of the MN, wherein the authentication request message carries the pre-authentication option; a second receiving unit, configured to receive an authentication response message that is sent by the AAA server, wherein the authentication response message carries a pre-authentication key used between a Candidate Authenticator (CA) and the MN; a second sending unit, configured to send the pre-authentication key to the MN; a storing unit, configured to store the pre-authorization key carried in the authentication response message received by the second receiving unit from the AAA server; and a binding unit, configured to establish a pre-authentication binding relationship between the CA and the MN after the determining unit determines the MN to be pre-authenticated, and set an authentication state of the MN as pre-authenticated according to the pre-authentication message.
 6. The pre-authentication device according to claim 5, further comprising: a discovering unit, configured to discover the CA of the MN; wherein the first sending unit is further configured to send a pre-authentication initiation message to the MN so that the MN selects the CA.
 7. A pre-authentication system, comprising: a pre-authentication device, configured to: receive a pre-authentication message that carries a pre-authentication option, determine a Mobile Node (MN) to be pre-authenticated according to the pre-authentication message, send an authentication request message to an Authentication, Authorization and Accounting (AAA) server to request authentication of the MN, wherein the authentication request message carries the pre-authentication option, receive an authentication response message that is sent by the AAA server, wherein the authentication response message carries a pre-authentication key used between a Candidate Authenticator (CA) and the MN, and send the pre-authentication key to the MN; and the AAA server, configured to: receive the authentication request message that is sent by the pre-authentication device, generate the pre-authentication key used between the CA and the MN according to the authentication request message, add the pre-authentication key to the authentication response message, and send the authentication response message to the pre-authentication device; wherein: the pre-authentication device is the CA of the MN, and the pre-authentication device is further configured to store the pre-authentication key between the CA and the MN, where the pre-authentication key is carried in the authentication response message received from the AAA server.
 8. The pre-authentication system according to claim 7, wherein: the pre-authentication device is further configured to locally establish a pre-authentication binding relationship between the pre-authentication device and the MN, and set an authentication state of the MN as pre-authenticated after determining the MN to be pre-authenticated. 